Recent popularization of the internet has diversified the use of personal computers, including processing of large volumes of moving image or sound data. With this trend, the demand for magnetic recording media, such as hard disks, with increased memory capacity has ever been increasing.
Currently spread hard disc drives adopt a longitudinal recording system in which a magnetic recording layer is magnetized in its running direction. It is said that the longitudinal recording system has limitations in density on account of the thermal fluctuation phenomenon that heat can cause data loss. In contrast, perpendicular magnetic recording in which a recording medium is magnetized in the direction perpendicular to the disk plane is expected as a next generation recording technology for achieving high density. A cobalt-chromium alloy (Co—Cr) is regarded as a promising magnetic material for realizing perpendicular magnetic recording.
In a hard disk drive, a magnetic disk is magnetized (recorded) with a magnetic head which flies from the magnetic disk on rotation of the magnetic disk. Thus, the magnetic head is prevented from coming into contact with the disk (head crash) and damaging the disk during high-speed rotation. The floating height of the magnetic head has been decreasing with the increasing recording density. Today, a floating height as small as 10 to 20 nm has been realized by using a magnetic disk having a magnetic layer on a super smooth and mirror-polished glass support.
The perpendicular magnetic recording is expected to achieve a further increased density. On the other hand, a higher density results in weaker signals of reproduction, which are less detectable. Therefore, in order to establish perpendicular magnetic recording technology on a hard disk drive, it is necessary to further decrease the distance between the disk and the head to improve reproduction ability.
However, since magnetic recording must be conducted in a non-contact mode so as to protect the disk from the shock of a head crash, it is difficult to reduce the flying height any more.
The state-of-the-art flexible disks have insufficient durability for perpendicular magnetic recording, and magnetic heads heretofore proposed for use in perpendicular magnetic recording are not fit for flexible disks.